Toilet cleaning articles adapted for placement in the toilet tank of a flush toilet and further adapted to release concentrated solutions of cleaning additives in response to a change in the level of the tank water are well known. Such devices that are adapted to form an air lock in the refill/discharge means are also well known.
Thus, for example, U.S. Pat. Nos. 4,261,957 and 4,301,556, each to Schimanski and U.S. Pat. No. 4,227,853 to McDuffy disclose dispensers comprising a basket to receive a solid cake or bar containing the active cleaning constituents, the basket having a plurality of holes for the intake and outflow of liquid.
U.S. Pat. Nos. 650,161 to Williams, et al., and 1,175,032 to Williams disclose dispensers provided with siphon means adapted to withdraw a given volume of solution from the dispenser. In these dispensers the inverted U-shaped siphon conduit extends well into the solution chamber, the cross-sectional area of said siphon tube to the cross-sectional area of the chamber being very small. Similar dispensers are disclosed in U.S. Pat. No. 969,729 to Smith and U.K. Pat. Nos. 1O,11O (1907) to Holloway; 2,125 (1908) to Berry; and 11,469 (1890) to Fleuss.
U.S. Pat. Nos. 4,171,546; 4,186,856, and 4,208,747 each to Dirksing; 4,251,012 to Owens, et al.; 4,281,421 to Nyquist, et al.; 4,216,027 to Wages, and U.K. Patent Application No. 2,090,884A each disclose passive dispensers wherein the product chamber solution is isolated from the tank water during quiescent periods by means of an air lock. In the '546 patent, the air lock is provided in the top of the chamber and straddles both an inlet conduit and an outlet conduit, the solution contained in the product chamber being evacuated therefrom through the discharge conduit in view of a pressure differential between the interior of said chamber and the atmosphere. The '856 patent operates in like manner, the dispenser having, however, an interior measuring cavity within the dispenser, said measuring cavity having a water inlet port. In the '747 patent, the dispenser comprises a product chamber, a reservoir for containing a quantity of the additive product solution, an inlet/discharge conduit having its lowermost end in fluid communication with the reservoir and its uppermost end in fluid communication with a siphon tube, an air trap disposed adjacent the inlet/discharge conduit, and an air vent in fluid communication with the reservoir and product chamber. During the filling of the '747 dispenser, tank water enters the siphon tube displacing air into said air trap, the entrapped air, after filling is complete, repositioning itself to the top of the siphon tube.
The '884A British Application discloses a dispensing device comprising an upper chamber with port means in fluid communication with the tank water, a lower chamber, serpentine first conduit means between said upper and lower chambers, an air lock being formed during refill in the serpentine conduit means, and inverted U-shaped conduit means disposed from the top of the lower chamber, an air lock being formed in the U-shaped conduit means during refill. In operation liquid in the upper chamber flows into the lower chamber in view of the head differential between the liquid in the dispenser and the tank water level, the liquid in the upper chamber displacing the solution in the lower chamber. The air lock in the serpentine conduit isolates the upper and lower chambers, and because the liquid in the upper chamber is substantially devoid of any solute, migration of solute from the upper chamber does not occur. In view of the air locks associated with each conduit, migration of solute or solution from the lower chamber also does not occur.